well that depends on how complicated you want it to get, on the harder side you could use a body heat sensor like the kind in motion detectors to get it to follow your heat signature. An easier way would be to build like a light seaking robot and instead of visible light it would seek a modulated signal from like an infrared keychain you hold. Just some ideas, if you have more specific questions about these just ask.

I cant believe that no-one has ever thought of this before? I mean shouldn't it be able to work off of an RF signal or an audio signal that is out of the reach of the human ear? i don't know a lot about what is available i am a design engineer in the automotive industry. i know more about sheetmetal stamping and plastic parts, but for some reason i have become addicted to knowing all i can about robotics and i can use all the help i can get. Please help!

i attempted to do this for my very first robot (which someday ill actually document).

the best way i know is to use the same method a bull uses to run down a matador . . . track the color red.

to be more specific, you wear a bright red shirt, and your robot has a camera running a very simple middle mass detection on the color red. the centroid is fed to your robot motors, and it will follow you.

ive got this to work on two of my robots.

the harder part is to get the robot to go where a human can go, something i have yet to accomplish . . .

I just thought of something. If you have played the game millipede you know that the segments of the body follow the head's path exactly,what if you could make a robot do the same thing, with you as the "head" and the robot as the "body segments"(say a GPS or something).